The present invention relates to a mask pattern correction method for forming a desired pattern on a wafer, a mask pattern creation system using the correction method, and a computer-readable recording medium.
The advance of recent semiconductor manufacturing techniques is remarkable, and semiconductors 0.20 μm in minimum processing size can be manufactured. This miniaturization is realized by rapid progress of a micro-pattern formation technique called photolithography. Photolithography includes a series of steps of creating a mask from an LSI design pattern, irradiating the mask with light, exposing a resist applied to a wafer to light in accordance with a pattern drawn on the mask by a projection optical system, developing the resist in accordance with the photosensitive distribution, and forming a resist pattern on the wafer. The resist pattern formed by these steps is used as a mask to etch an underlayer, thereby forming an LSI pattern on the wafer.
When the pattern size was much larger than the limit resolution of the projection optical system, it was possible to directly draw as a design pattern the planar shape of an LSI pattern to be formed on a wafer, create a mask pattern faithful to the design pattern, transfer the mask pattern onto a wafer by the projection optical system, etch an underlayer, and form a pattern almost conforming to the design pattern. However, as patterns continue to shrink in feature size, the optical proximity effect becomes prominent. With a mask created in conformity with a design pattern, a pattern formed on a wafer is different from the design pattern. Adverse effects along with this are becoming serious.
For example, on a line & space (L/S) pattern, exposed dose amounts for finishing a isolated pattern and dense pattern present on the same mask plane with desired sizes are different depending on the respective patterns, so an common dose margin between isolated and dense pattern margin necessary in the lithography step cannot be obtained. To solve this, a method of moving the pattern edge position in advance so as to finish a planar shape obtained upon exposure with a predetermined exposure amount, within a predetermined size regardless of the pattern density is proposed. This is called correction of the optical proximity effect. This correction methods are roughly classified into two schemes.
According to one scheme, the edge moving amount is set as a rule in advance, and the edge position of design data is moved in accordance with the rule (ruse-based scheme). This method sets the edge moving amount as a rule in accordance with the distance between an edge to be corrected and its nearest edge. The edge moving amount can therefore be described by a simple rule, and the correction time is relatively short.
To realize high-precision correction of the optical proximity effect, the edge moving amount must be changed in accordance with not only the distance to the nearest edge but also the line widths of a pattern to be corrected and its nearest pattern, and the like. Of such methods, a method of changing the edge moving amount in accordance with the line width of a pattern to be corrected is reported in Proc. SPIE 2197 (1994) 361 or the like. This method is proved to be effective for increasing the correction precision.
However, to change the edge moving amount in accordance with the line width of the nearest pattern, a more complicated correction rule is required. A test pattern shape and measurement technique necessary for rule setting become very cumbersome accordingly.
For this reason, a simulation-based correction method as the other scheme is effective. According to this method, a range necessary for obtaining the optimal edge moving amount is determined from design data having various pattern layouts, and the optimal edge moving amount can be calculated within the range by a light intensity simulation technique. Hence, the simulation-based scheme need not set any complicated rule as described above, and can perform high-precision correction by only determining parameter values used for a model for predicting experimental results at higher precision.
The simulation-based scheme is very effective for increasing the correction precision. However, this scheme executes calculation for calculating the correction amount in accordance with each pattern layout, so the correction time is often very long.